An internal combustion engine (abbreviated below as an engine) of an automobile or the like mixes fuel injected from a fuel injection device and air introduced via an intake air pipe to generate a combustible gas mixture and burns the combustible gas mixture in the cylinder. It is known that the mixture state of fuel injected from the fuel injection device and air significantly affects the performance of this type of engine and, in particular, the atomization of fuel injected from the fuel injection device is an important factor governing the performance of the engine.